The invention pertains to casters and caster systems wherein a constant biasing force is imposed upon the caster wheel for load supporting purposes.
Casters are widely used to support material handling trucks, tables, bins, receptacles, pallet lift trucks, and the like. In some instances, it is desirable that the caster be spring mounted so that shocks may be absorbed, or the weight supported by a specific caster can be adjusted. Where a plurality of casters are simultaneously employed for support purposes, it is usually desirable that each caster exerts the same force upon the load in order to equalize wheel wear and produce uniform load support.
Where casters are individually spring supported, it is very difficult to individually adjust casters so that equal forces are supported by each caster when a plurality of casters are used together for load bearing purposes.
It is an object of the invention to provide a caster which is vertically adjustable, and wherein the caster load characteristics can be accurately adjusted.
A further object of the invention is to provide a vertically adjustable caster wherein the vertical position of the caster wheel is adjusted by fluid pressure, such as oil pressure, and wherein the pressure upon the fluid supporting the caster can be varied.
Yet another object of the invention is to provide a caster system wherein a plurality of casters are used for load bearing purposes, and wherein the load supporting force of each caster is identical.
An additional object of the invention is to provide a caster system utilizing a plurality of casters wherein a pressurized fluid is used to simultaneously vertically adjust all of the casters in the system, and wherein uniform pressure is employed in all casters for load bearing purposes, and such pressure can be easily adjusted.
Casters constructed in accord with the inventive concepts utilize a caster housing having a support plate mounted thereon for mounting the caster. The caster housing includes an internal cylindrical chamber defining an expansible chamber motor, and a piston is reciprocally mounted within the chamber. A lever mounted upon the caster housing pivotally supports the caster wheel for vertical adjustment, and the caster piston is affixed to the lever to apply the desired vertical force to the caster wheel. In the disclosed embodiment, one end of the lever is pivotally mounted to the caster housing, while the caster wheel is mounted upon the other end of the lever, and the lever center region is affixed to the caster piston.
The fluid pressure within the caster expansible chamber motor, preferably a hydraulic oil, is pressurized by a pressure unit comprising a cylindrical chamber having a piston reciprocally mounted therein. The pressure unit piston is biased toward the associated chamber by a compression spring whose degree of compressive force is adjustable by a compressing screw.
A plurality of casters constructed in accord with the invention may be interconnected by a common conduit system wherein the internal expansible chambers of each piston housing are in communication, and also in communication with the fluid pressurizing unit. In this instance, each of the caster levers, and caster wheel, is subjected to a common fluid pressurizing force from the pressurizing unit, and thereby a constant biasing force on the load may be imposed by the plurality of interconnected casters regardless of number.